error types

util/errors.go

@@ -0,0 +1,37 @@
+package util
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/codegangsta/cli"
+)
+
+// PrintError is used for printing information when an error is encountered.
+func PrintError(c *cli.Context, err error) {
+	w := c.App.Writer
+	switch err.(type) {
+	case ErrMissingFlag, ErrFlagFormatting:
+		fmt.Fprintf(w, "%s", err.Error())
+		fmt.Fprintf(w, "Usage: %s\n", c.Command.Usage)
+	}
+	os.Exit(1)
+}
+
+// ErrMissingFlag is used when a user doesn't provide a required flag.
+type ErrMissingFlag struct {
+	Msg string
+}
+
+func (e ErrMissingFlag) Error() string {
+	return fmt.Sprintf("Missing flag: %s\n", e.Msg)
+}
+
+// ErrFlagFormatting is used when a flag's format is invalid.
+type ErrFlagFormatting struct {
+	Msg string
+}
+
+func (e ErrFlagFormatting) Error() string {
+	return fmt.Sprintf("Invalid flag formatting: %s\n", e.Msg)
+}